Question

The Indian peacock is well known for its extravagant iridescent blue-green tail plumage. When courting the peahen, peacocks will fan out their tail feathers to make an impressive display. Birds possessing at least one copy of the dominant gene (P_) will have the peacock plumage but birds bearing the homozygous recessive genotype pp will have the peahen plumage. Peahens are usually dull gray or brown in color regardless of genotype. Peahens never develop the peacock tail plumage and those bearing the genotype W_ will lay white eggs but those with the genotype ww lay brown eggs.

1. Which of the following best describes the inheritance pattern of peacock tail plumage? (1 pt)

___      a. X-linked           b. Y-linked           c. Sex limited           d. Sex-influenced             e. Answer not shown

2. A peafowl breeder will obtain the best price for birds that lay brown eggs or birds with iridescent blue-green tail plumage. He mated birds with a heterozygous genotype and obtained 10 eggs. What is the probability of obtaining two brown egg-laying birds and 3 birds with iridescent blue-green tail plumage? All calculations must be shown to obtain full pts. (8 pts)

Answer 1

1. Answer: Option C is correct
Given information,
PP/Pp = Tail feathers
pp = No tail feathers
It is an autosomal trait i.e. the gene is located on the autosomes.
X-linked alleles are denoted as X^P or X^p
Sex limited traits are expressed only in one sex and never in other sex.
Sex-influenced traits are expressed in both sexes however to a different degree in individual gender.

2. Answer: Option C is correct
Given information,
Parental cross: PpWw X PpWw
Progeny:
P_W_ = 9 = Brown eggs and bright plumage
P_ww = 3 = White eggs and bright plumage
ppW_ = 3 = Brown eggs and dull plumage
ppww = 1 = White eggs and dull plumage